A Negative Bird
The crow is seen as a negative omen only recently and mostly in Europe.

Celts
For the Celts, the crow was sacred and meant the flesh torn by fighting. As he eats carrion, the welsh poetry uses the metaphor "the crow pierced you" to say "you have died". They thought crows escorted the sun during his nocturnal path, that is to say in Hell. So they were a symbol of evil, contrary to swanns, symbolizing purity.

Babylon
In Babylon, the crow was the name of the 13th month of the calendar, and he had a very negative value.

Greeks
For the Greeks, the crow was too gossipy. That's why Athena replaced him with the owl, to stay with her. The crow was also devoted to Apollo. The god sent him to the aquatic world, to bring back water. The crow discovered a fig tree whose fruits were not ripe yet, so he waited near the tree to eat ripe figs instead of accomplishing his task . He was punished for his disobediance and egotism : Apollo placed him in the constellations, but the hydra prevented him from drinking the cup : he is condemned to thirst.

Bible
In the Bible, the crow is sent by Noah to search earth after the flood. But the crow didn't told Noé that the flood was finished. So he is considered selfish.
Saint Golowin thought that in Paradise, the crows had multicoloured wings. But after Adam and Eve were driven away from the Paradise, the crows started to eat carrion. So they became black-feathered. At the end of time, the crows will find their beauty again and sing harmoniously to praise God.

Middle-Ages
In the Middle-Ages, it was said that crows neglect their young; as he eats carrions, he is seen as a bad omen.

India
In India, in the Mahâbhârata, the messengers of death are compared to crows. In Laos, the water soiled by crows can't be used for ritual purification.

It is mostly in nomadic civilisations (hunters and fishers) that the crow has a positive meaning. He lost this meaning with the sedentarisation and the agrarian developpement.

Tlingit Indians
For Tlingit Indians (North-West of the Pacific), the crow is the main divine character. He organises the world, gives civilisation and culture, creates and freeze the sun.

Haïda Indians
For Haïda indians (North-western coast of the Canada), the crow will steal the sun from the sky's master, to give it to the earth's people. Raven has also a magic canoe : he can make it change its size, from the pine needle size, to big enough to contain the whole universe.

North America
In North America, he is the personnification of the Supreme Being. When he flaps his wings he creates the wind, the thunder and the lightning.

Mithra's Cult
In Mithra's cult, he can fight evil spells.

Scandinavians Legends
Scandinavians legends show two crows, perched on Odin's seat : Hugi, the Spirit, and Munnin, the Memory. They symbolize the principle of creation. In the same way, these birds are the companions of Wotan ("the God with the crows").

Celts
The crow was sacred for the Celts. He was associated to the creation of Lugdunum (Lyon), city of the God Lug. Lug is the great solar god. He has the form of a crow and is assimilated to Apollo.

Bible
The crow is also in the Bible: he brings bead to man, alone in the desert.Prophet Elie, Saint Paul hermit, Saint Antoine... Saint Vincent had been defended by crows against the attack of carnivores; the crow is also seen at Saint Benoît's feet and in Saint Oswald's hands. Here, he symbolizes divine providence.
He is also linked to Saints Boniface and Meinrad : their two tame crows allowed to find their corpses.

Asiatic Mythology
The crow has also a role in the asiatic mythology : in China and in Japan, he shows love and filial gratitude.According to chinese legends, ten red crows with three paws flew away from the East Blackberry Tree to bring light to the world. But they brought an unbearable heat to the Earth. Yi The Good Archer killed nine of
them, and saved the world. The last Crow is now in the Sun.

The major meaning of this black bird is to be a guide and the Gods' messenger.

Black Africa
In Black Africa, the crow warns men that dangers are menacing them. The crow is their guide and a protector spirit.

Mayas
For Mayas, he is the messenger of the God of lightning and thunder.

Celtic Civilisation
In Celtic civilisation, he has prophetic functions. Bodb, Goddess of the war, takes the form of a raven to observe the battlefields. The crows' fly and cawings told the future. The crow was also linked to Bran, God of the sailors (bran means crow in gaelic) : the sailors had crows on their boats. They released them at sea. They flied in the direction of the earth. The same idea is in the Bible (after the flood Noah released first a crow),in India and in Norway.

Greece>
In Greece the crow foretold the future : a raven stood near the Pythie of Delphes during her prediction. It is generally said in Greece that the white crow guides messengers. This function of messenger of the Gods (especially Apollo's messenger), may have its origin in a greek legend. Coronis was unfaithful to Apollo, and a crow informed him. According to Ovide, the crow was originally white. Apollo made him become black to punish him for bringing bad news. Apollo even took a form of crow to guide Santorin's people to Cyrena.
And two crows showed Alexander the Great the road to Amon's sanctuary.

Scandinavian Mythology
Hugi and Munnin (Thought and Memory), are Odin's companions. In scandinavian mythology, they travel all over the world and come back to tell Odin all the events that happens on earth.

Mithraic
In the mithraic cult, Sol(the God Sun) entrust the crow with telling Mithra to sacrifice the bull.

Japan
In Japan, crows are also divine messengers, and in China they are the faerie queen Hsi-Wang-Mu's messengers. They also bring her food and are a good omen.